Extracted images: Small-Scale Sand Filters¶
Printed revision: March 2021.
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Original Mistral crops are preserved byte for byte. A crop can be a figure, table, equation, or other visual; no visual content is inferred as a numerical rule. Record and table associations use the same PDF page unless a direct image placeholder is identified. Nearby OCR excerpts are context, not verified captions.
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Mistral ID: img-0.jpeg. Extraction bundle(s): 2023_BMP_9_9_Small_Scale_Sand_Filters. Original page | Image file
Tables on the same PDF page: Table 1
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# 9.9 SMALL-SCALE SAND FILTERS (GI)
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Small-scale sand filters are stormwater management systems designed to maximize the removal of pollutants from stormwater runoff. A small-scale sand filter consists of a pre-treatment zone and a treatment zone, which includes the sand bed as the filter media and its underlying materials. Pollutants are treated through settling, filtration and adsorption by the sand bed prior to discharging stormwater r
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# Applications
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Pursuant to N.J.A.C. 7:8-5.2(a)(2), the minimum design and performance standards for groundwater recharge, stormwater runoff quality and stormwater runoff quantity at N.J.A.C. 7:8-5.4, 5.5 and 5.6 shall be met by incorporating green infrastructure in accordance with N.J.A.C. 7:8-5.3.
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Small-scale sand filters may be designed to convey storm events larger than the Water Qualit
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ds for groundwater recharge, stormwater runoff quality and stormwater runoff quantity at N.J.A.C. 7:8-5.4, 5.5 and 5.6 shall be met by incorporating green infrastructure in accordance with N.J.A.C. 7:8-5.3.
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Small-scale sand filters may be designed to convey storm events larger than the Water Quality Design Storm (WQDS); however, regardless of the design storm chosen, all small-scale sand filters must be designed for stability and capacity in accordance with the Standards for Soil Erosion and Sediment Control in New Jersey, as required by N.J.A.C. 7:8 Stormwater Management rules.
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-scale sand filters must be designed for stability and capacity in accordance with the Standards for Soil Erosion and Sediment Control in New Jersey, as required by N.J.A.C. 7:8 Stormwater Management rules.
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Small-scale sand filter systems, since they must be designed to infiltrate into the subsoil, may be used to meet the groundwater recharge requirements. For more information on computing ground water recharge, see Chapter 6: Groundwater Recharge.
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To merit the approved TSS removal rate of 80%, small-scale sand filters must be designed to treat the WQDS and in accordance with a
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they must be designed to infiltrate into the subsoil, may be used to meet the groundwater recharge requirements. For more information on computing ground water recharge, see Chapter 6: Groundwater Recharge.
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To merit the approved TSS removal rate of 80%, small-scale sand filters must be designed to treat the WQDS and in accordance with all of the following criteria.
# Design Criteria
## Basic Requirements
The following illustrations depict the basic components and the various zones through which stormwater runoff travels.
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Profile View – Small-Scale Sand Filter Basics
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cordance with all of the following criteria.
# Design Criteria
## Basic Requirements
The following illustrations depict the basic components and the various zones through which stormwater runoff travels.
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Profile View – Small-Scale Sand Filter Basics
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Plan View – Small-Scale Sand Filter Basics
The following design criteria must all be met in order to receive the 80% TSS removal rate for this BMP. It is critical that all small-scale sand filters are designed in accordance with these criteria in order to ensure proper operation, to maximize the functional life of the system and to ensure public safety.
## Contributory Drainage Area
- Pursuant to N.J
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scharge, computed on the basis of the net area of opening through rack;
Constructed of rigid, durable and corrosion-resistant material; and
Designed to withstand a perpendicular live loading of 300 lbs./sf.
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- An overflow grate is designed to prevent obstruction of the overflow structure. If an outlet structure has an overflow grate, the grate must comply with the following requirements:
The overflow grate must be secured to the outlet structure but removable for emergencies and maintenance;
The overflow grate spacing must be no greater than 2 inches across the smallest dimension; and
The overflow grate m
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- The minimum diameter of any overflow orifice is 2.5 inches.
- Blind connections to down-gradient facilities are prohibited. Any connection to down-gradient stormwater management facilities must include access points such as inspections ports and manholes, for visual inspection and maintenance, as appropriate, to prevent blockage of flow and ensure operation as intended. All entrance points must adher
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The following cross-section view provides another view of a small-scale sand filter.
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Cross Section View – Small-Scale Sand Filter
## Requirements for Extended Detention Option
A small-scale sand filter may be constructed as part of an on-line, combination system to provide extended detention for larger storms. Such a system could include a level-graded infiltration zone such as that defined by a smaller contour, oval or other discrete area within the basin bottom. Runoff up to the WQD
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1\ \text{ft/12 in})} = 7.41\ \text{hr}
$$
The resulting surface area could be achieved with a 50 ft by 30.4 ft sand bed. Illustrations for this example are shown below and continue on the following page.
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Example: Small-Scale Sand Filter in Plan and Profile Views
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Example: Small-Scale Sand Filter in Cross-Section View
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## Considerations
When planning a small-scale sand filter, consideration should be given to soil characteristics, depth to the groundwater table, sensitivity of the region and inflow water quality. It is also important to note that the use of small-scale sand filters is recommended in this manual only where the WQDS or smaller storm events are contained below the first outlet control structure. Use o